Name
EXT_shader_image_load_formatted
Name Strings
EXT_shader_image_load_formatted
Contact
Jeff Bolz, NVIDIA Corporation (jbolz 'at' nvidia.com)
Pat Brown, NVIDIA Corporation (pbrown 'at' nvidia.com)
Contributors
Status
Complete.
Version
Last Modified Date: March 11, 2014
Revision: 1
Number
XXX
Dependencies
This extension is written against the OpenGL 4.3 specification
(Compatibility Profile).
This extension is written against version 4.30 of the OpenGL
Shading Language Specification.
This extension interacts with GL_NV_bindless_texture.
This extension interacts with GL_EXT_shader_image_load_store and
NV_gpu_program5.
Overview
ARB_shader_image_load_store (and OpenGL 4.2) added support for
random access load and store from/to texture images, but due to
hardware limitations, loads were required to declare the image
format in the shader source. This extension relaxes that
requirement, and the return values from imageLoad can be format-
converted based on the format of the image binding.
New Procedures and Functions
None.
New Tokens
None.
Additions to Chapter 8 of the OpenGL 4.3 (Compatibility Profile) Specification
(Rasterization)
Modify Section 8.25 Texture Image Loads and Stores, p. 284
(modify the bullet describing the format layout mismatch)
- the format layout qualifier for an image variable used for an image load
(if specified) or atomic operation does not match the format of the image
unit, according to table 8.33; or
(modify the first paragraph on p. 285)
Image variables used for shader loads, stores, and atomics may be declared
with a format layout qualifier. If the format layout qualifier is present,
then the format must match the format of the associated image unit, as
enumerated in table 8.33, otherwise the access is considered to involve a
format mismatch, as described above. Image variables used for atomics must
be declared with a format layout qualifier. Image variables used only for
loads and stores may be declared without a format layout qualifier, in which
case the format of the image is inferred from the associated image unit.
New Implementation Dependent State
None.
New State
None.
Additions to the AGL/GLX/WGL Specifications
None.
GLX Protocol
None.
Modifications to the OpenGL Shading Language Specification, Version 4.30
Including the following line in a shader can be used to control the
language features described in this extension:
#extension GL_EXT_shader_image_load_formatted :
where is as specified in section 3.3.
New preprocessor #defines are added to the OpenGL Shading Language:
#define GL_EXT_shader_image_load_formatted 1
Modify Section 4.4.6.2 Format Layout Qualifiers (p. 71)
(modify the second paragraph on p.71)
Any image variable used for image atomic operations must specify a format
layout qualifier; it is a compile-time error to pass an image uniform
variable or function parameter declared without a format layout qualifier
to an image atomic function.
Delete the last paragraph on p.71: (Uniforms not qualified with
must have a format layout qualifier. ...)
Errors
Dependencies on NV_bindless_texture
When an image variable uses a bindless image handle, the format of the
image is inferred from the handle rather than "from the associated image
unit".
Dependencies on EXT_shader_image_load_store and NV_gpu_program5
Modify Section 2.X.4, Program Execution Environment
Instr- Modifiers
uction V F I C S H D Out Inputs Description
------- -- - - - - - - --- -------- --------------------------------
LOADIM 50 X X X X - F v vs,i image load
(Add to "Section 2.X.6, Program Options" of the NV_gpu_program4 extension,
as extended by NV_gpu_program5:)
+ Formatted Image Loads (EXT_shader_image_load_formatted)
If a program specifies the "EXT_shader_image_load_formatted" option, it
may use the "F", "U", or "S" data types with the "LOADIM" opcodes to
perform formatted image load operations.
Modify Section 2.X.8.Z, (LOADIM: Image Load)
LOADIM supports an optional base data type (formatted) or storage modifier
(unformatted). Formatted image loads operate as described in Section 8.25.
Unformatted image loads are treated as invalid unless the storage modifier
matches the image unit format, as described in Table X.3. The base data
type of the result vector is derived from the storage modifier. The single
operand is always interpreted as a signed integer vector.
Class Supported Modifers
------- -------------------
4x32 F32X4, S32X4, U32X4
2x32 F32X2, S32X2, U32X2
1x32 F32, S32, U32
1x16 S16, U16
1x8 S8, U8
Table X.3, Supported Storage Modifiers. Unformatted image operations
are considered invalid unless the storage modifier is compatible with
the "Class" entry for the image unit format, as described in Table
8.33.
Issues
Revision History
Rev. Date Author Changes
---- -------- -------- -----------------------------------------------
1 01/28/14 jbolz Internal revisions.